Alright, to clear up the misconception i think most of the posters in this thread have regarding co2, it does not necessarily mean that it will increase the fps. If mags come out that use the co2 capsules then the fps is entirely dependent on how the internal regulator inside the mag is set. Meaning that the FPS could very possibly be even lower than with propane if the manufacturer decided that.
CO2 compresses into a liquid at 800-900psi which means no airsoft gun except a custom made few (Piper's Miniguns, strafers etc) could possibly run off unregulated co2. This is also another reaso